APDRP SCHEME , WESCO
Technical Specification for Distribution Transformers ( 11/0.4KV )
PART 1: GENERAL
1.
SCOPE
This specification covers the design, engineering, manufacture, testing, supply, delivery, offloading and
performance requirements of 11/0.433kV distribution transformers for outdoor use in the networks of
the WESCO. The transformers shall be double wound, three phase, oil immersed with ONAN cooling.
The ratings required are 100kVA, 250kVA and 500kVA.
The transformer shall conform in all respects to highest standards of engineering, design, workmanship,
this specification and the latest revisions of relevant standards at the time of offer and the Purchaser
shall have the power to reject any work or material, which, in his judgement, is not in full accordance
therewith.
2.
STANDARDS
Except where modified by this specification, the transformers shall be designed, manufactured and tested in
accordance with the latest editions of the following standards. The Bidder may propose alternative standards,
provided it is demonstrated that they give a degree of quality and performance equivalent to or better than
the referenced standards. Whether to accept or reject any alternative standard shall be adjudged by the
Purchaser. The Bidder shall furnish a copy of the alternative standard proposed along with the bid. If the
alternative standard is in a language other than English, an English translation shall be submitted with the
standard. In the case of conflict the order of precedence shall be 1) IEC or ISO Standards, 2) Indian
Standards, 3) other alternative standards.
IEC / ISO
Indian
Standard
IEC 71
IEC 76
IEC 137
Insulation Coordination.
IS 2026
Power Transformers.
IS 1180-Part 2
Outdoor Three Phase Transformers up to 100kVA 11kV - Sealed
Type
IS 2099
Bushings for Alternating Voltages above 1000 V.
IEC 156
IEC 296
IEC 354
Subject
Method of determining Electric Strength of Insulating Oils.
IS 335
Specification for Unused Mineral Insulating Oils for Transformers
and Switchgear.
IS 6792
Method of determination of electric strength of insulating oils.
IS 6600
Loading Guide for oil immersed Transformers
IEC 437
Radio Influence Voltage Measurement.
IEC 551
Determination of Transformer and Reactor Sound Levels.
IEC 616
Terminal and Tapping markings for power transformers.
IEC 722
Guide to the Lightning and Switching impulse
Power Transformers and Reactors.
ISO 1460/BS 729
IS 2629
Galvanizing.
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testing of
APDRP SCHEME , WESCO
Technical Specification for Distribution Transformers ( 11/0.4KV )
This list is not to be considered exhaustive and reference to a particular standard or recommendation in
this specification does not relieve the Supplier of the necessity of providing the goods complying with
other relevant standards or recommendations.
3.
SERVICE CONDITIONS
The service conditions shall be as follows:
•
maximum altitude above sea level
1,000m
•
maximum ambient air temperature
50°C
•
maximum daily average ambient air temperature
35°C
•
minimum ambient air temperature
•
maximum temperature attainable by an object exposed to the sun
60°C
•
maximum yearly weighted average ambient temperature
32°C
•
maximum relative humidity
100%
•
average number of thunderstorm days per annum (isokeraunic level)
•
average number of rainy days per annum
•
average annual rainfall
•
maximum wind pressure
4.
SYSTEM CONDITIONS
5°C
70
120
150 cm
94.3 kg/m²
The equipment shall be suitable for installation in supply systems of the following characteristics:
•
Frequency
50Hz
•
Nominal system voltages
33 kV
11 kV
400/230 V
•
Maximum system voltages:
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33kV System
36 kV
11kV System
12 kV
LV System
476 V
APDRP SCHEME , WESCO
Technical Specification for Distribution Transformers ( 11/0.4KV )
•
Minimum LV voltage
•
Nominal short circuit levels:
•
340 V
33kV System
25 kA
11kV System
12.5 kA
33kV System
170 kV
11kV System
75 kV
33kV System
70 kV
11kV System
28 kV
Insulation levels:
1.2/50 µs impulse withstand
(positive and negative polarity):
•
Power frequency one minute withstand
(wet and dry)
LV System
•
Neutral earthing arrangements:
3 kV
33kV System
solidly earthed
11kV System
solidly earthed
LV System
solidly earthed
PART 2: TECHNICAL
5.
TYPE OF TRANSFORMER
The transformers shall be double wound, three phase, oil immersed, 11/0.433kV, 50 Hz with natural oil and
air cooling (ONAN).
The design of the tank, fittings, bushings, etc. shall be such that it will not be necessary to keep the
transformer energised to prevent deterioration as the transformers may be held in reserve, outdoors, for
many years.
6.
RATINGS
The following ratings are covered by this specification:
• 100kVA;
• 250kVA;
• 500kVA
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APDRP SCHEME , WESCO
Technical Specification for Distribution Transformers ( 11/0.4KV )
All of the above are required with HV and LV bushing terminations. In addition, some 500 kVA
transformers are required with HV and LV outdoor cable terminations.
The transformer shall be capable of supplying a continuous load equal to its kVA rating, under the following
conditions:
• the rated secondary voltage held constant by increasing the primary voltage to allow for
regulation at all tap positions;
•
constant flux regulation;
•
continuous steady load;
•
design maximum ambient air temperature of 50°C;
• 55oC average winding temperature rise and 50°C top oil temperature rise for conventional
breathing transformes
• 55oC average winding temperature rise and 45°C top oil temperature rise for sealed type
transformes
The transformer may be overloaded during emergency up to 150% of its continuous rating in accordance
with IEC Publication 354 or IS 6600. Bushings, tap changer and other current-carrying parts shall also be
designed for this condition.
7.
VOLTAGE RATIO AND TAPPING RANGE
The transformers shall have the following ratio and tapping range:
• the nominal voltage ratio shall be 11,000/433V;
• tolerance on the voltage ratio shall be ±0.5%;
• for 100kVA transformers a tap-changer is not required.
• for transformers rated 250 kVA and above, taps shall be provided in the high voltage
winding for voltage variation from Tap 1 (+2.5%) to Tap 4 (-5.0%) in equal steps of 2.5%. Tap
No.2 shall be the principal tap.
The bidder shall state in the technical schedule, the percentage regulation at full load, power factor 1.0 and at
full load, power factor 0.85 lagging. The primary voltage variation is based on a winding temperature of
75°C.
8.
IMPEDANCE VOLTAGE
The guaranteed value of impedance voltage measured at 75°C and on the principal tap (subject to a tolerance
of +10% and no negative tolerance, as specified in IEC 76 / IS 2026) shall be 4.0% for all units.
9.
SHORT CIRCUIT RATINGS
The transformer shall be capable of withstanding the thermal and dynamic effects of short circuits, as
specified in IEC 76-5: Ability to withstand short circuits.
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APDRP SCHEME , WESCO
Technical Specification for Distribution Transformers ( 11/0.4KV )
Each transformer shall be capable of withstanding for 2 seconds a bolted metallic short circuit on the
terminals of either winding with rated voltage on the other winding and the tap-changer in any position.
If short circuit tests have been carried out on the particular design of transformer offered, the test results shall
be supplied with the bid.
10.
VECTOR GROUP
The transformers shall be connected delta-star, in accordance with vector group reference Dyn11 of IEC 76 /
IS 2026.
The LV neutral shall be brought out to a terminal bushing, which shall be identical to the phase bushings in
all respects.
11.
LOSSES
No-load loss and load loss values are to be submitted and losses will be capitalized at the rates and added to
bid price for the purpose of comparing tenders.
Losses shall be measured during routine tests. In the event of either the no-load loss or load loss exceeding
their guaranteed values, as stated in the technical data schedules, the relevant rate above shall be applied to
the excess and the resulting amount shall be deducted from the Contract Price.
Transformers are likely to be rejected if losses exceed the declared values by more than 10%.
12.
FLUX DENSITY
The flux density at any point of the magnetic circuit when the transformer is connected on the center tap and
operating at normal voltage and frequency shall be stated and shall not exceed 1.6 Tesla. The transformer
must be capable of operating at 10% over voltage at frequency of 48 Hz without saturation occurring or
the flux density exceeding 1.9 tesla.
13.
INSULATION LEVELS
The following insulation levels as defined in IEC 76-3 / IS 2026 Insulation levels and dielectric tests shall
apply:
Table 2: Transformer insulation level
HV Winding
LV Winding
Basic Impulse voltage Level (kV) (1.2/50
mic.sec. wave )
75
Not
Applicable
Power Frequency voltage withstand level, Wet
and Dry (kV)
28
3
Bushings and terminals shall be adequate for the winding insulation tests, and shall flash over externally
before puncture or internal failure can occur.
14.
NOISE LEVEL
The average noise level of the transformers shall not exceed the following values:
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APDRP SCHEME , WESCO
Technical Specification for Distribution Transformers ( 11/0.4KV )
• 100kVA transformers
51 dB
• 250 kVA and 500 kVA transformer
57 dB
The measurements shall be carried out in accordance with IEC 551 at a distance of 300mm from the
envelope of the transformer.
15.
RADIO INFLUENCE VOLTAGE
The maximum radio influence voltage shall be 250µV, measured as specified in IEC 437.
16.
TAP CHANGING CHARACTERISTICS
Tap changing and the tap changing mechanism shall have the following characteristics:
• tap changing shall be carried out with the transformer off circuit;
• tap positions shall be numbered as follows:
Tap 1
+ 2.5 %
Tap 2
0 % (Principal Tap)
Tap 3
- 2.5 %
Tap 4
- 5.0 %
• provision shall be made for locking of the tap switch handle by using a padlock with 6 mm diameter hasp
to be furnished by Purchaser; and
• tap change handles shall be fitted with gasketed covers, so that sealing of the transformer under
normal conditions is independent of the switch shaft gland.
• CORE AND WINDINGS
The core shall be constructed from high grade, non-ageing, cold rolled grain oriented silicon steel
laminations or superior material.
The core and winding shall be capable of withstanding shocks during transport, installation and service.
Provision shall be made to prevent movement of the core and windings relative to the tank during these
conditions and also during short circuits.
The design shall avoid the presence of pockets which would prevent the complete emptying of the tank
through the drain valve.
16.1.
Windings
The winding insulation shall be free from insulating compounds which are liable to soften, ooze out, shrink
or collapse. It shall be non catalytic and chemically inert in transformer oil during normal service.
The stacks of windings are to receive adequate shrinkage treatment.
The windings and connections are to be braced to withstand shocks during transport, switching, short circuit
or other transient conditions.
The windings shall be uniformly insulated and the LV neutral points shall be insulated for full voltage.
The winding conductor shall be of electrolytic copper. As an alternative, however, aluminium winding
conductor may be offered for sizes up to 100 kVA. The current density shall not exceed 2.5 Amps per sq.
mm for copper, or 1.5 Amps for aluminium at normal full load current.
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APDRP SCHEME , WESCO
Technical Specification for Distribution Transformers ( 11/0.4KV )
17.
BUSHINGS AND TERMINATIONS
17.1. Bushings
Bushings shall be of the outdoor type and easily replaceable. Cemented in types will not be acceptable. They
shall be sufficiently robust to withstand normal transport and erection hazards and shall conform to IEC 137
/ IS 3347 and 2099.
All bushings shall have a minimum creepage distance of 25 mm/kV and shall have a continuous rating of
200% of the transformer rating. The protected creepage distance shall not be less than 50% of the total.
The following minimum 11kV clearances shall be provided :
Enclosed
External
Phase to phase
127mm
255mm
Phase to earth
76mm
140mm
The 11 kV bushings of transformers shall be provided with a bi-metallic terminal connector or suitable
device to receive 25 - 100 sq.mm. AAAC or ACSR conductor directly without any bi-metallic action.
The secondary bushings of 100kVA shall be fitted with non ferrous threaded terminals. With the exception
of brass the terminals shall be protected from atmospheric deterioration by suitable tinning or by some other
approved coating. For transformers of rating 250kVA and higher the LV bushings shall be fitted with
terminal plates.
The number of 17 mm diameter holes to be drilled in these plates depends on the size of transformer and
shall be :
kVA Rating
No. of Holes
250
2
500
3
The terminals are to be supplied with one 16mm bolt, one conic spring washer, one matching flat washer,
one nut and one lock nut for each hole in the terminal plate.
17.2.
Bushing Labels
The HV bushings shall be labelled U, V and W and the LV bushings u, v, w and n. Marking letters shall be
at least 12mm high. The means of marking shall be either:
♦
engraved metal plate; or
♦
etched anodized aluminum.
Phase identification by adhesive stickers shall not be acceptable.
If labeling is to be carried out on the tank, it is preferred that one plate be used rather than individual
markings for each phase, in order to prevent incorrect phase markings.
Labels shall conform to the requirements of the section on Labels in this specification.
17.3.
Cable Terminations
Some 500kVA transformers will be required with HV and LV cable terminations. These transformers
are to be fitted with weatherproof cable entry boxes suitable for connection of the following sizes of
cables :
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APDRP SCHEME , WESCO
Technical Specification for Distribution Transformers ( 11/0.4KV )
High Voltage Side
Transformer
Size ( kVA )
Low Voltage Side
Cable Size
No. of
Cable Size
Range
Cables
( sq. mm )
( sq. mm )
per phase
500
25 - 70 Al XLPE
1
Type of cable
Three core cable
with steel armour
300s Al PVC
No. of
Cables
No. of
per phase
Cables
neutral
3
3
Single core
cable with out
armour
The design of the cable boxes shall be such that all tests can be carried out on the transformer in the
factory and dielectric tests can be carried out on the cable on site, simply and without the need for
complicated procedures. The 11kV cable box must be suitable for bolted heat shrink terminations in
air.
17.4.
Earthing Terminals
All transformers shall be provided with two earthing terminals comprising an M12 ISO metric bolt and nut
which shall be non ferrous. It shall include a spring washer and a lock washer.
18.
TANK FABRICATION
Transformers shall have bolted tank covers and may be either of the sealed type, or non-sealed type. Nonsealed transformers may be designed with or without conservators.
Transformer tanks of all types shall be designed so that the completed transformer can be lifted and
transported without permanent deformation or oil leakage. Stiffeners provided for rigidity should be so
designed that there is no accumulation of water.
The tank shall be fabricated of mild steel with minimum thickness of 3mm. Top and bottom covers of the
tank shall have a minimum thickness of 5 mm. Thickness below this value will be considered only in
exceptional cases, such as where superior material or special protective finishes are offered. The bidder shall
provide full information about any such special material or finish, including any field experience.
The transformer tank and the top cover shall be designed in such a manner as to leave no external pockets in
which water can lodge, or any internal pocket where air/gas can accumulate.
All sealing washers/gaskets shall be made of oil and heat resistant nitrile rubber or neoprene bonded cork
seals suitable for temperature as stipulated in this specification. Surfaces at gasketed joints shall be such that
an even face is presented to the gasket, thereby eliminating the necessity for the gasket to take up surface
irregularities.
All pipes, radiators, stiffeners or corrugations which are welded to the tank wall shall be welded externally
and shall be double welded wherever possible. All welds shall be stress relieved.
18.1.
Pressure Relief Device
Transformers of 250 kVA and above shall be fitted with a pressure relief device in the form of explosion
vent or pressure relief valve. The tenderer shall state the pressure at which it is designed to operate.
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APDRP SCHEME , WESCO
Technical Specification for Distribution Transformers ( 11/0.4KV )
18.2.
Oil Level Gauge
A suitable oil level gauge shall be fitted on all types of transformer and so located that it can be easily read
from ground level. The gauge shall be graduated for temperatures of 0°C, +45°C and +90°C. Where a
conservator tank is fitted the gauge shall be on the conservator.
19.
CONSERVATORS AND BREATHERS.
The conservator tank shall be so designed and located as to eliminate any trapping of air in the transformer
or pipe work. It shall be inclined at an angle of about 5 degrees to the horizontal towards the drain plug and
the pipe connecting the main tank to the conservator should project about 20mm above the bottom of the
conservator so as to create a sump for the collection of impurities. Minimum oil level corresponding to 0°C
shall be well above the sump level.
All transformers shall be fitted with a silica gel breather of weatherproof design at a convenient height with
oil seal at the bottom to isolate the silica gel from the atmosphere. The breather shall be connected to the
conservator tank.
20.
FITTINGS
The following standard fittings shall be provided :
• rating, diagram and terminal marking plate.
• two earthing terminals
• lifting lugs
• pressure relief device / explosion vent as required
• silica gel breather (for all non-sealed transformers)
• filling and drain / sampling plugs (note that for transformer sizes up to 100kVA, a single drain
/ filling plug shall consist of a 20mm pipe inside the transformer tank, starting from the bottom
and projecting to the top cover with a hermetically sealed / welded plug).
• a magnetic or prismatic oil level gauge for all transformers.
The fittings and accessories listed are indicative only and any other fittings and accessories which are
generally required for satisfactory operation of the transformer are to be provided without any extra cost.
21.
SURGE ARRESTER ATTACHMENTS
Transformers shall be fitted with means of attaching a surge arrester support bracket, consisting of brackets
or extensions to the cover plate. These shall be located opposite each HV bushing and shall be drilled with
holes of 13mm diameter for fixing the arrester brackets. The final arrester position must provide a nominal
100 mm clearance between bushing and arrester.
22.
TRANSFORMER OIL
The transformers shall be supplied filled with class 1 mineral oil conforming to IEC 296 or IS 335
whichever is more stringent. The complete first filling shall be of new oil free from inhibitors and additives.
The dielectric strength of the oil shall not be less than 60kV when tested in accordance with
IS 6792,
1972.
If an anti-oxidant inhibitor is recommended, its use shall be subject to the purchaser’s approval.
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APDRP SCHEME , WESCO
Technical Specification for Distribution Transformers ( 11/0.4KV )
23.
RATING AND CONNECTION PLATE
Each transformer shall be provided with a rating plate of weatherproof material showing the following items
indelibly marked:
• type of transformer;
• standard to which it is manufactured (preferably IEC 76);
• manufacturer's name;
• transformer serial number;
• year of manufacture;
• rated frequency in Hz (50);
• rated voltages in kV (11/0.433);
• Number of phases (3);
• rated power in kVA;
• type of cooling (ONAN);
• rated currents in A;
• vector group symbol (Dyn11);
• 1.2/50µs wave impulse voltage withstand level in kV;
• power frequency withstand voltage in kV;
• impedance voltage at rated current and frequency in percentage;
• load loss in kW at rated current;
• no-load loss in kW at rated voltage and frequency;
• continuous ambient temperature at which ratings apply in °C (45);
• top oil and winding temperature rise at rated load in °C;
• winding connection diagram;
• total weight in kg;
• volume of oil in litres;
• weight of core and windings in kg; and
• name of the purchaser (Grid Corporation of Orissa Ltd.).
The rating plate shall conform to the requirements of the section on Labels in this specification.
24.
MOUNTING ARRANGEMENT
The underbase of all transformers shall be provided with two 75 x 40mm channels, 460mm long with holes
of 14mm diameter at a centre to centre distance of 415mm to make them suitable for fixing on a platform or
plinth.
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APDRP SCHEME , WESCO
Technical Specification for Distribution Transformers ( 11/0.4KV )
25.
SURFACE TREATMENT
The transformer tank and accessories shall be adequately protected against corrosion. The inside of the tank
shall be painted with an approved oil resisting varnish. External surfaces shall be painted as specified in the
section on Surface Treatment in this specification, or to a superior standard. Any alternative surface
treatment shall be subject to approval of the Purchaser.
An alternative quotation shall be made for the external surfaces of the transformer tank and its steel
attachments to be hot dip galvanised as specified in the section on Surface Treatment of this specification. In
the case of transformers rated 100kVA and higher, the galvanising shall be followed by one coat of
weatherproof enamel paint to a minimum thickness of 30µm. The colour shall be grey, colour No. 631 of IS
5. Sufficient pretreatment of the zinc surface should be carried out as necessary in order to guarantee long
life adhesion.
26.
SUPPRESSION OF HARMONICS.
The transformer shall be designed with attention to the suppression of harmonic voltages, especially the third
and fifth.
27.
TESTS
27.1.
Routine Tests
Routine tests shall be carried out on all transformers and the tests shall be conducted in accordance with IEC
76 / IS 2026 where this is applicable. In addition tank tests in accordance with IS:1180 Part 2 shall be carried
out.
The following routine measurements and tests shall be carried out:
a) measurement of winding resistance at principal tap and two extreme taps;
b) voltage ratio measurement and check of polarity and vector group at all tap positions. Bushing positions
shall have permanent markings at this stage of production;
c) measurement of impedance voltages /short circuit impedance at rated current and frequency at principal
tap;
d) measurement of load loss at full load and 75°C;
e) measurement of no-load loss and no-load currents at full, 90% and 110% voltages;
f) induced overvoltage withstand test: 22kV for 60 sec on the HV windings;
g) separate source voltage withstand tests on HV and LV windings:
h) air pressure test for sealed transformers. ( IS:1180 Part 2)
i) Magnetic balance test.
j) Polarization Index test. Index shall be not less than 1.5.
k) oil leakage test: The criterion of leakage shall be discoloration by oil of whitewash applied externally to
suspected parts at an oil temperature of 90°C or other method approved by the purchaser;
l) galvanising tests, where applicable.
Bushings and oil shall be subject to the following routine tests.
m) Bushing routine tests: in accordance with IEC 137/IS 3347;
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APDRP SCHEME , WESCO
Technical Specification for Distribution Transformers ( 11/0.4KV )
n) oil dielectric and moisture content test: conforming to IEC 156 or IS 335.
Routine test certificates shall include in addition to the test results, the purchaser's order number, the
transformer serial number, outline drawing number and transformer kVA rating.
27.2.
Type Tests
The measurements and tests shall be carried out in accordance with the standard specified in each case in
table 6 below:
Table 6: Transformer type tests
Type Test
Standard
Temperature Rise Test
IEC 76/IS 2026
Impulse Voltage Withstand Test, Including Full Waves and
Chopped Waves as listed below
IEC 76/IS 2026
Noise Level Measurement
IEC 551
Short Circuit Test.
IEC 76 / IS 2026
Air Pressure Test ( Sealed type transformers only)
IS:1180 Part 2.
In accordance with IEC 76-3 the following sequence of impulses shall be applied:
one full wave at 50% BIL;
one full wave at 100% BIL;
one chopped wave at 50% BIL;
two chopped waves at 100% BIL; and
two full waves at 100% BIL.
PART 3 GENERAL PARTICULARS AND GUARANTEES
28.
COMPLIANCE WITH SPECIFICATION
The transformers shall comply in all respects with the requirements of this specification. However, any
minor departure from the provisions of the specification shall be disclosed at the time of tendering in the
Non Compliance Schedule in Part 3 of this document.
The mass and dimensions of any item of equipment shall not exceed the figures stated in the Schedules.
29.
COMPLIANCE WITH REGULATIONS
All the equipment shall comply in all respects with the Indian Regulations and acts in force.
The equipment and connections shall be designed and arranged to minimise the risk of fire and any
damage which might be caused in the event of fire.
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APDRP SCHEME , WESCO
Technical Specification for Distribution Transformers ( 11/0.4KV )
29.1.
Inspection and Testing
The Purchaser shall have free entry at all times, while work on the contract is being performed, to all parts of
the manufacturer's works which concern the processing of the equipment ordered. The manufacturer shall
afford the Purchaser without charge, all reasonable facilities to assure that the equipment being furnished is
in accordance with this specification.
The equipment shall successfully pass all the type tests and routine tests referred to in Clause 42, Part 2 and
those listed in the most recent edition of the standards given in Clause 2, Part 1 of this specification.
The Purchaser reserves the right to reject an item of equipment if the test results do not comply with the
values specified or with the data given in the technical data schedule.
Type tests shall be carried out at an independent testing laboratory or be witnessed by a representative of
such laboratory or some other representative acceptable to the Purchaser. Routine tests shall be carried out
by the Supplier at no extra charge at the manufacturer's works.
Type tests may be dispensed with at the Purchaser's discretion if the Supplier furnishes evidence to the
Purchaser's satisfaction that the relevant tests have already been performed on identical equipment. In this
case test certificates shall be submitted with the bid for evaluation.
The Purchaser may witness routine and type tests. In order to facilitate this, the Supplier shall give the
Purchaser a minimum of four weeks notice that the material is ready for testing. If the Purchaser does not
indicate his intention to participate in the testing, the manufacturer may proceed with the tests and shall
furnish the results thereof to the Purchaser.
Full details of the proposed methods of testing, including connection diagrams, shall be submitted to the
Purchaser by the Supplier for approval, at least one month before testing.
All costs in connection with the testing, including any necessary re-testing, shall be borne by the Supplier
who shall provide the Purchaser with all the test facilities which the latter may require, free of charge. The
Purchaser shall have the right to select the samples for test and shall also have the right to assure that the
testing apparatus is correct. Measuring apparatus for routine tests shall be calibrated at the expense of the
Supplier at an approved laboratory and shall be approved by the Purchaser.
The Supplier shall be responsible for the proper testing of the plant or materials supplied by subsuppliers to the same extent as if the work, plant or materials were completed or supplied by the
Supplier.
Any cost incurred by the Purchaser in connection with inspection and re-testing as a result of failure of the
equipment under test or damage during transport or offloading shall be to the account of the Supplier.
The Supplier shall submit to the Purchaser five signed copies of the test certificates, giving the results of the
tests as required. No materials shall be dispatched until the test certificates have been received by the
Purchaser and the Supplier has been informed that they are acceptable.
The test certificates must show the actual values obtained from the tests, in the units used in this
specification, and not merely confirm that the requirements have been met.
In the case of components for which specific type tests or routine tests are not given in Part 2, or in the
quoted standards in Clause 2, of this specification, the Supplier shall include a list of the tests normally
required for these components. All materials used in the Contract shall withstand and shall be certified to
have satisfactorily passed such tests.
No inspection or lack of inspection or passing by the Purchaser’s Representative of equipment or
materials whether supplied by the Supplier or sub-supplier, shall relieve the Supplier from his liability
to complete the contract works in accordance with the contract or exonerate him from any of his
guarantees.
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APDRP SCHEME , WESCO
Technical Specification for Distribution Transformers ( 11/0.4KV )
29.2.
Guarantee
The Supplier shall guarantee the following :
•
Quality and strength of materials used;
• Satisfactory operation during the guarantee period of five year from the date of commissioning,
or 72 months from the date of acceptance of the equipment by the Purchaser following delivery,
whichever is the earlier;
•
Performance figures as supplied by the tenderer in the schedule of guaranteed particulars;
• The offered surface treatment shall protect the treated metal from corrosion for a period of not
less than five years from the date of delivery.
30.
SUBMITTALS
The following shall be required with each copy of the bid :
• completed technical data schedule;
• descriptive literature giving full technical details of equipment offered;
• outline dimension drawing for each major component, general arrangement drawing showing
component layout and general schematic diagrams;
• type test certificates, where available, and sample routine test reports;
• detailed reference list of customers already using equipment offered during the last 5 years with
particular emphasis on units of similar design and rating;
• details of manufacturer's quality assurance standards and programme and ISO 9000 series or
equivalent national certification;
• deviations from this specification. Only deviations approved in writing before award of contract
shall be accepted;
• list of recommended spare parts and consumable items for five years of operation with prices
and spare parts catalogue with price list for future requirements.
30.1.
Technical Data Schedule for 100kVA Three Phase Transformer
ITEM
NO.
DESCRIPTION
1
GENERAL
UNIT
SPECIFIED
Name and address of manufacturer
International or national standards with
which the transformer and accessories
comply
IEC -76
IS-2026
IS-1180
Nominal frequency
Hz
50
nominal power rating
kVA
100
- 14 -
BIDDER’S
OFFER
APDRP SCHEME , WESCO
Technical Specification for Distribution Transformers ( 11/0.4KV )
ITEM
NO.
DESCRIPTION
UNIT
SPECIFIED
Maximum continuous power rating
kVA
100
Nominal primary voltage
kV
11
Nominal secondary voltage
V
433
Type of cooling
ONAN
Vector Group
Dyn11
Winding polarity
2
3
IMPEDANCE VOLTAGE
Impedance at rated current and frequency
%
Resistance component of impedance
%
Reactance component of impedance
%
4
SHORT CIRCUIT PERFORMANCE
Short circuit current withstand capability
kA
Duration
sec
2 sec
kV rms
28
kV rms
3
X/R ratio
4
INSULATION LEVELS
a) Separate source power frequency
withstand voltage
HV winding
LV winding
b) Induced overvoltage withstand level
HV winding
kV rms
LV winding
kV rms
c) Full wave 1.2/50 µs lightning impulse
withstand level HV winding
5
kV peak 75
OVERLOAD / TEMPERATURE RISE
Duration of overload: 25%
min
Duration of overload: 50%
min
Design maximum ambient temperature
o
500
Design average ambient temperature
o
350
Maximum winding temperature rise
o
550
Top oil temperature rise
o
450 sealed.
Maximum hot spot temperature at ambient
temperature of 45oC
o
C
C
C
C
- 15 -
C
BIDDER’S
OFFER
APDRP SCHEME , WESCO
Technical Specification for Distribution Transformers ( 11/0.4KV )
ITEM
NO.
6
DESCRIPTION
UNIT
Maximum temperature gradient
o
SPECIFIED
C/mm
CURRENT AND FLUX DENSITY
Maximum current density at full load current.
HV winding
A/mm2
2.5(Cu)/1.5(Al)
LV winding
2
A/mm
2.5(Cu)/1.5(Al)
Tesla
1.6
Maximum Flux density at rated voltage and
frequency.
Maximum flux density at 12kV and 48 Hz
7
8
9
Tesla
GUARANTEED LOSSES
Core losses at rated voltage and frequency.
W
Winding losses at rated current at 75°C
W
No load current (at 11kV) as percentage of
full load current.
%
Regulation at 75 °C :full load at PF =1
full load, PF=0.85
CORE AND WINDINGS
%
%
Silicone steel of core:
manufacturer/supplier
type/grade
Conductor for HV winding:
manufacturer/supplier
type/grade
conductor material
Conductor for LV winding:
manufacturer/supplier
type/grade
conductor material
Cross section area of HV winding
CRGO
mm2
Cross section area of LV winding
mm2
CLEARANCES
Minimum HV Phase to Phase clearance:
in oil
mm
127
outside oil.
mm
255
in oil
mm
76
outside oil
mm
140
Minimum HV clearance Phase to earth
Insulation material HV winding:
manufacturer/supplier
type/grade:
- 16 -
BIDDER’S
OFFER
APDRP SCHEME , WESCO
Technical Specification for Distribution Transformers ( 11/0.4KV )
ITEM
NO.
DESCRIPTION
UNIT
SPECIFIED
Insulation material LV winding:
manufacturer/supplier
type/grade:
10
BUSHINGS AND TERMINALS
HV bushings:
manufacturer/supplier
type/grade
LV bushings:
manufacturer/supplier
type/grade
Type of HV terminal
Metal used for terminal studs
Tightening bolt diameter
mm
Type of atmospheric protection
Minimum phase to phase clearance
mm
255
Minimum phase to earth clearance
mm
140
Type of LV terminal
Metal used for terminal
Tightening bolt diameter
mm
Type of atmospheric protection
Minimum phase to phase clearance
mm
Minimum phase to earth clearance
mm
Type of earth terminal material
Non ferrous
Bolt and Nut
Are spring and lock washers included?
11
12
Yes/No Yes
TRANSFORMER OIL
IEC:296/IS:335
Oil:
class-1
mineral oil
manufacturer/supplier
type/grade
Quantity of oil
litres
Breakdown Voltage at the time of filling.
kV
Moisture content at the time of filling
ppm
60
TRANSFORMER TANK
Sealed Type
Yes/No Yes
Type of steel
Mild steel
Grade of steel
High Grade
- 17 -
BIDDER’S
OFFER
APDRP SCHEME , WESCO
Technical Specification for Distribution Transformers ( 11/0.4KV )
ITEM
NO.
DESCRIPTION
UNIT
SPECIFIED
tank steel
mm
3
top cover
mm
5
bottom cover
mm
5
cooling surfaces
mm
Minimum thickness of :
Top oil temperature corresponding to
100 kN/sq.m pressure
o
Steady load to give top oil temp (50 C
ambient)
Steady load to give top oil temp (50 oC
ambient and solar radiation of 1,200 W/m2)
o
C
kVA
kVA
Pressure for actuating relief device fitted
Corrosion protection
type/grade
supplier
Thickness of coating
13
14
15
Paint/
Galvanising
microns 200/64
DIMENSIONS AND WEIGHTS
Overall width
mm
Overall height
mm
Overall depth
mm
Weight of core
kg
Weight of tank
kg
Weight of windings
kg
Weight of oil at 200C
kg
Total weight of transformer, ready for
service
kg
Shipping weight of transformer
kg
EFFICIENCY
Efficiencies at 75oC at unity power factor
a)
at full load
b)
at 3/4 full load
c)
at 1/2 full load
d)
at 120% full load
e)
Load at which maximum
efficiency occurs
f)Maximum efficiency
INSULATION RESISTANCE
Values at 30oC
- 18 -
%
%
%
%
kVA
%
BIDDER’S
OFFER
APDRP SCHEME , WESCO
Technical Specification for Distribution Transformers ( 11/0.4KV )
ITEM
NO.
DESCRIPTION
UNIT
Megaohms
Megaohms
Megaohms
HV to Earth
LV to Earth
HV to LV
- 19 -
SPECIFIED
BIDDER’S
OFFER
APDRP SCHEME , WESCO
Technical Specification for Distribution Transformers ( 11/0.4KV )
30.2.
Technical Data Schedule for 250kVA Three Phase Transformer
ITEM
NO.
DESCRIPTION
1
GENERAL
UNIT
SPECIFIED
Name and address of manufacturer
International or national standards with
which the transformer and accessories
comply
IEC -76
IS-2026
IS-1180
Nominal frequency
Hz
50
nominal power rating
kVA
250
Maximum continuous power rating
kVA
250
Nominal primary voltage
kV
11
Nominal secondary voltage
V
433
Type of cooling
ONAN
Vector Group
Dyn11
Winding polarity
2
3
IMPEDANCE VOLTAGE
Impedance at rated current and frequency
%
Resistance component of impedance
%
Reactance component of impedance
%
4
SHORT CIRCUIT PERFORMANCE
Short circuit current withstand capability
kA
Duration
sec
2 sec
kV rms
28
kV rms
3
X/R ratio
4
INSULATION LEVELS
a) Separate source power frequency
withstand voltage
HV winding
LV winding
b) Induced overvoltage withstand level
HV winding
kV rms
LV winding
kV rms
c) Full wave 1.2/50 µs lightning impulse
withstand level HV winding
- 20 -
kV peak 75
BIDDER’S
OFFER
APDRP SCHEME , WESCO
Technical Specification for Distribution Transformers ( 11/0.4KV )
ITEM
NO.
DESCRIPTION
5
OVERLOAD / TEMPERATURE RISE
6
UNIT
SPECIFIED
Duration of overload: 25%
min
Duration of overload: 50%
min
Design maximum ambient temperature
o
500
Design average ambient temperature
o
350
Maximum winding temperature rise
o
550
Top oil temperature rise
o
450 sealed.
500 unsealed
Maximum hot spot temperature at ambient
temperature of 45oC
Maximum temperature gradient
o
C
C
C
C
C
o
C/mm
CURRENT AND FLUX DENSITY
Maximum current density at full load current.
HV winding
A/mm2
2.5(Cu)/1.5(Al)
LV winding
2
A/mm
2.5(Cu)/1.5(Al)
Tesla
1.6
Maximum Flux density at rated voltage and
frequency.
Maximum flux density at 12kV and 48 Hz
7
8
Tesla
GUARANTEED LOSSES
Core losses at rated voltage and frequency.
W
Winding losses at rated current at 75°C
W
No load current (at 11kV) as percentage of
full load current.
%
Regulation at 75 °C : full load at PF =1
full load, at PF=0.85
CORE AND WINDINGS
%
%
Silicone steel of core:
manufacturer/supplier
type/grade
Conductor for HV winding:
manufacturer/supplier
type/grade
conductor material
CRGO
Copper
Conductor for LV winding:
manufacturer/supplier
type/grade
conductor material
Copper
Cross section area of HV winding
- 21 -
2
mm
BIDDER’S
OFFER
APDRP SCHEME , WESCO
Technical Specification for Distribution Transformers ( 11/0.4KV )
ITEM
NO.
9
DESCRIPTION
UNIT
Cross section area of LV winding
mm2
SPECIFIED
CLEARANCES
Minimum HV Phase to Phase clearance:
in oil
mm
127
outside oil.
mm
255
in oil
mm
76
outside oil
mm
140
Minimum HV clearance Phase to earth
10
Insulation material HV winding:
manufacturer/supplier
type/grade:
Insulation material LV winding:
manufacturer/supplier
type/grade:
BUSHINGS AND TERMINALS
HV bushings:
manufacturer/supplier
type/grade
LV bushings:
manufacturer/supplier
type/grade
Type of HV terminal
Metal used for terminal studs
Tightening bolt diameter
mm
Type of atmospheric protection
Minimum phase to phase clearance
mm
255
Minimum phase to earth clearance
mm
140
Type of LV terminal
Metal used for terminal
Tightening bolt diameter
mm
Type of atmospheric protection
Minimum phase to phase clearance
mm
Minimum phase to earth clearance
mm
Type of earth terminal material
Non ferrous
Bolt and Nut
Are spring and lock washers included?
- 22 -
Yes/No Yes
BIDDER’S
OFFER
APDRP SCHEME , WESCO
Technical Specification for Distribution Transformers ( 11/0.4KV )
ITEM
NO.
DESCRIPTION
11
TRANSFORMER OIL
IEC:296/IS:335
Oil:
class-1
mineral oil
12
UNIT
manufacturer/supplier
type/grade
Quantity of oil
litres
Breakdown Voltage at the time of filling.
kV
Moisture content at the time of filling
ppm
SPECIFIED
60
TRANSFORMER TANK
Sealed Type
Yes/No Sealed or
unsealed
Type of steel
Mild steel
Grade of steel
High Grade
Minimum thickness of :
tank steel
mm
3
top cover
mm
5
bottom cover
mm
5
cooling surfaces
mm
Top oil temperature corresponding to
100 kN/sq.m pressure if sealed type.
o
Steady load to give top oil temp (50 C
ambient)
Steady load to give top oil temp (50 oC
ambient and solar radiation of 1,200 W/m2)
Pressure for actuating relief device fitted
Corrosion protection
type/grade
supplier
Thickness of coating
13
o
C
kVA
kVA
Paint/
Galvanising
microns 200/64
DIMENSIONS AND WEIGHTS
Overall width
mm
Overall height
mm
Overall depth
mm
Weight of core
kg
Weight of tank
kg
Weight of windings
kg
Weight of oil at 200C
kg
Total weight of transformer, ready for service kg
- 23 -
BIDDER’S
OFFER
APDRP SCHEME , WESCO
Technical Specification for Distribution Transformers ( 11/0.4KV )
ITEM
NO.
14
15
DESCRIPTION
UNIT
Shipping weight of transformer
kg
EFFICIENCY
Efficiencies at 75oC at unity power factor
a)
at full load
b)
at 3/4 full load
c)
at 1/2 full load
d)
at 120% full load
e)
Load at which maximum
efficiency occurs
f)Maximum efficiency
INSULATION RESISTANCE
Values at 30oC
HV to Earth
LV to Earth
HV to LV
- 24 -
%
%
%
%
kVA
%
Megaohms
Megaohms
Megaohms
SPECIFIED
BIDDER’S
OFFER
APDRP SCHEME , WESCO
Technical Specification for Distribution Transformers ( 11/0.4KV )
30.3.
Technical Data Schedule for 500kVA Three Phase Transformer
ITEM
NO.
DESCRIPTION
1
GENERAL
UNIT
SPECIFIED
Name and address of manufacturer
International or national standards with
which the transformer and accessories
comply
IEC -76
IS-2026
IS-1180
Nominal frequency
Hz
50
nominal power rating
kVA
500
Maximum continuous power rating
kVA
500
Nominal primary voltage
kV
11
Nominal secondary voltage
V
433
Type of cooling
ONAN
Vector Group
Dyn11
Winding polarity
2
3
IMPEDANCE VOLTAGE
Impedance at rated current and frequency
%
Resistance component of impedance
%
Reactance component of impedance
%
4
SHORT CIRCUIT PERFORMANCE
Short circuit current withstand capability
kA
Duration
sec
2 sec
kV rms
28
kV rms
3
X/R ratio
4
INSULATION LEVELS
a) Separate source power frequency
withstand voltage
HV winding
LV winding
b) Induced overvoltage withstand level
HV winding
kV rms
LV winding
kV rms
c) Full wave 1.2/50 µs lightning impulse
withstand level HV winding
- 25 -
kV peak 75
BIDDER’S
OFFER
APDRP SCHEME , WESCO
Technical Specification for Distribution Transformers ( 11/0.4KV )
ITEM
NO.
DESCRIPTION
5
OVERLOAD / TEMPERATURE RISE
6
UNIT
SPECIFIED
Duration of overload: 25%
min
Duration of overload: 50%
min
Design maximum ambient temperature
o
500
Design average ambient temperature
o
350
Maximum winding temperature rise
o
550
Top oil temperature rise
o
450 sealed.
500 unsealed
Maximum hot spot temperature at ambient
temperature of 45oC
Maximum temperature gradient
o
C
C
C
C
C
o
C/mm
CURRENT AND FLUX DENSITY
Maximum current density at full load current.
HV winding
A/mm2
2.5(Cu)/1.5(Al)
LV winding
2
A/mm
2.5(Cu)/1.5(Al)
Tesla
1.6
Maximum Flux density at rated voltage and
frequency.
Maximum flux density at 12kV and 48 Hz
7
8
Tesla
GUARANTEED LOSSES
Core losses at rated voltage and frequency.
W
Winding losses at rated current at 75°C
W
No load current (at 11kV) as percentage of
full load current.
%
Regulation at 75 °C : full load PF =1
full load, PF=0.85
CORE AND WINDINGS
Silicone steel of core:
manufacturer/supplier
type/grade
Conductor for HV winding:
manufacturer/supplier
type/grade
conductor material
Conductor for LV winding:
manufacturer/supplier
type/grade
conductor material
Cross section area of HV winding
- 26 -
%
%
CRGO
mm2
BIDDER’S
OFFER
APDRP SCHEME , WESCO
Technical Specification for Distribution Transformers ( 11/0.4KV )
ITEM
NO.
9
DESCRIPTION
UNIT
Cross section area of LV winding
mm2
SPECIFIED
CLEARANCES
Minimum HV Phase to Phase clearance:
in oil
mm
127
outside oil.
mm
255
in oil
mm
76
outside oil
mm
140
Minimum HV clearance Phase to earth
10
Insulation material HV winding:
manufacturer/supplier
type/grade:
Insulation material LV winding:
manufacturer/supplier
type/grade:
BUSHINGS AND TERMINALS
HV bushings:
manufacturer/supplier
type/grade
LV bushings:
manufacturer/supplier
type/grade
Type of HV terminal
Metal used for terminal studs
Tightening bolt diameter
mm
Type of atmospheric protection
Minimum phase to phase clearance
mm
255
Minimum phase to earth clearance
mm
140
Type of LV terminal
Metal used for terminal
Tightening bolt diameter
mm
Type of atmospheric protection
Minimum phase to phase clearance
mm
Minimum phase to earth clearance
mm
Type of earth terminal material
Non ferrous
Bolt and Nut
Are spring and lock washers included?
- 27 -
Yes/No Yes
BIDDER’S
OFFER
APDRP SCHEME , WESCO
Technical Specification for Distribution Transformers ( 11/0.4KV )
ITEM
NO.
DESCRIPTION
11
TRANSFORMER OIL
IEC:296/IS:335
Oil:
class-1
mineral oil
12
UNIT
manufacturer/supplier
type/grade
Quantity of oil
litres
Breakdown Voltage at the time of filling.
kV
Moisture content at the time of filling
ppm
SPECIFIED
60
TRANSFORMER TANK
Sealed Type
Yes/No Sealed or
unsealed
Type of steel
Mild steel
Grade of steel
High Grade
Minimum thickness of :
tank steel
mm
3
top cover
mm
5
bottom cover
mm
5
cooling surfaces
mm
Top oil temperature corresponding to
100 kN/sq.m pressure if sealed type.
o
Steady load to give top oil temp (50 C
ambient)
Steady load to give top oil temp (50 oC
ambient and solar radiation of 1,200 W/m2)
o
C
kVA
kVA
Pressure for actuating relief device fitted
Corrosion protection
type/grade
supplier
Thickness of coating
13
Paint/
Galvanising
microns 200/64
DIMENSIONS AND WEIGHTS
Overall width
mm
Overall height
mm
Overall depth
mm
Weight of core
kg
Weight of tank
kg
Weight of windings
kg
0
kg
Weight of oil at 20 C
Total weight of transformer, ready for service kg
- 28 -
BIDDER’S
OFFER
APDRP SCHEME , WESCO
Technical Specification for Distribution Transformers ( 11/0.4KV )
ITEM
NO.
14
15
DESCRIPTION
UNIT
Shipping weight of transformer
kg
EFFICIENCY
Efficiencies at 75oC at unity power factor
a)
at full load
b)
at 3/4 full load
c)
at 1/2 full load
d)
at 120% full load
e)
Load at which maximum
efficiency occurs
f)Maximum efficiency
INSULATION RESISTANCE
Values at 30oC
HV to Earth
LV to Earth
HV to LV
31.
- 29 -
%
%
%
%
kVA
%
Megaohms
Megaohms
Megaohms
SPECIFIED
BIDDER’S
OFFER